Tunable badiofbequency tbansfobmeb



July 15, 1930. G. H. BRowNlNG Er AL 1,770,456

TUNALE RADIOFREQUENCY TRANSFORHER Original Filed Dec. l, 1924 Patented July 15, 1930 A UNITED STATES PATENT OFFICE GLENN H. BBOWNING, OF 1IIN'CHES'JEEB.,` AND FREDERICK H. BRAKE, OF WATEBTOWN,

IASSACHUSETTS, ASSIGNOBS TO NATIONAL COMPANY, INC., OF MALDEN, MASSA- CHUSETTS, A CORPORATION OF IASSACHUSETTS TUNABLE RADIOFBEQUENC'Y '.lBANSFOBMEBV Application illed December 1, 19M, Serial No. 753,821. Renewed Kay 10, 192B.

Our invention aims to provide improvements in radio frequenc transformers.

It has been determine after much experimentationand careful calculation, that in a transformerof the character mentioned the position of theV primary ycoil with respect to the secondary coil is critical for maximum amplification, and this invention has for its object to provide a transformer embodying therein an arrangement of primary and secondary coils capable of producing a much greater amplification than it vhas heretofore been possible toobtain in transformers of this character.

Another object of the invention is to provide a transformer for a tunable radio frequency apparatus, in which the primary coil is hunched up or concentrated and located in such a position relatively to the secondary coil as to minimize the capacity between the coils, thereby making it possible to produce an apparatus in which a greater transfer of energy will take place than has heretofore been ossible.

Sti l another object of the invention is to provide a rotor or tertiary coil in inductive relation to the seconda coil of the transformer, and connected 1n one circuit of a multiple element device such as a vacuum tube to lower the effective resistance of the secondary coil of the transformer, thus increasing the transfer of ener taking place in the radio frequency trans ormer, or the rotor coil may serve as an untuned antenna coil.

Referring to the drawings:

Figure 1 represents a side elevation of a tunable radio frequency transformer embodying our invention, certain portions thereof being broken away and illustrated in section.

Fig. 2 is an end elevation of the transformer as viewed from the right, Fig. 1.

Fig. 3 is an end elevation of the transformer as viewed from the left, Fig. 1.

Like numerals refer to like parts throughout the several views of the drawings.

In the drawings, 5 represents a tube constructed of bakelite, or similar insulation material, and extending around the periphery of said tube adjacent to one end thereof is an annular groove 6 in which a primary coil 7 is wound. The primary coil 7 is hunched up or concentrated and entirely confined within the groove 6 and consists of approximately 24 turns of number 30 D. C. C. wire, the opposite ends of which are connected to binding posts 8 and 9 mounted in the tube 5. I

Extending, around the periphery of the tube 5- outside of the primary coil 7 and continuing longitudinally therebeyond is a Sicondary coil 10,- preferably consisting of approximately 77 turns of N o. 20 D. S. C. wire, the opposite ends of 'which are connected to binding posts 11 and 12 mounted in the tube 5.

The coils 7 and 10 are preferably separated by a thin `layer of suitable sheet material 13, such as paper. A loop 14 is formed in the secondary coil 10 at a suitable point thereon in order that a wire may be secured thereto. The primary and secondary coils are so positioned relatively to each other that the rimary coil will be located near the first ew turns of the secondary coil and near the low potential end of the latter.

Located within the tube 5 adjacent to the opposite end thereof from that at which the primary coil 7 is located and adjacent to the high potential end of the secondary coil 1() is a short length of tube 15,v the latter being rigidl secured to a rod 16 which is mounted to roc in bearing members 17 and 18 mounted in the tube 5. A suitable knob 19 is provided for the rod 16. The tube 15 has grooves 20 and 21 extending around the periphery thereof in which a rotor or tertiary coil 22 is located, a portion of said coil being located in each of the grooves 20 and 21 and in inductive relation to the secondary coil 10. The coil 22 preferably consists of approximately 30 turns of No. 30 D. C. C. wire, the opposite ends of which are secured to terminals 23 and 24 mounted in the tube 15. The terminals 23 and 24 are connected by suitable 'wires 25 and 26 respectively to binding posts 27 and 28 mounted in the tube 5. The kvarious binding posts of the transformer are connected to the di'erent elements of'a tunable radio frequency type of a paratus in a manner well known to those s illed in the art.

By using a transformer, as h ereinbefore described, it is possible to obtain a maximum amount of amplification and the operator is enabled to tune the apparatus sharply, easily cutting out local broadcasting stations and tuning in upon the distant stations.

It will be understood that a transformer embodying therein a primary and secondary coil, arranged as hereinbefore described and eliminating the rotor or tertiary coil may be employed without departing from the spirit of this invention, such construction being set forth in certain of the appended claims. When, however, the rotor or tertiary coil is employed, being connected in the radio apparatus in one circuit of a multiple element device, such as a vacuum tube, the effective resistance of the secondary coil of the transformer is lowered, thus increasing the transfer of energy taking place in the radio frequency transformer.

While we have shown and described a preferred embodiment of our invention we do not wish to be limited thereby, our invention being best defined in the following claims.

We claim:

l. A tunable radio frequency transformer comprising, in combination, a member provided With a groove therein, a primary coil Wound in a bunch around said member and confined within said groove and a secondary coil positioned in inductive relation to said primary coil, said primary coil being located near the low potential end of said secondary coil.

2. A tunable radio frequency transformer comprising, in combination, a member provided virith a groove therein, a primary coil wound in a bunch around said member and confined Within said oove and a secondary coil positioned in ingirictive relation to said primary coil, said primary coil being located within the first turns of Wire at the low potential end of said secondary coil.

3. A tunable radio frequency transformer comprising, in combination, a member provided with an annular groove extending around the periphe thereof, a primary coil Wound around sai member and confined within said groove, and a secondary coil positioned in inductive relation to said prima coil, said prima coil being located at the low potential en of said secondary coil.

4. A tunable radio frequency transformer comprising, in combination, a tube of insulating material provided with an annular groove extending around the periphery thereof, a primary coil Wound around said tube and confined Within said groove, and a secondary coil Wound around said tube outside of said primary coil and containing longitudinally therebeyond, said 'primary coil being located withinthe first turns of wire a't the low potential end of said secondary coil.

5. A tunable radio frequency transformer comprising, in combination, a tube of insulating material provided with an annular groove extending around the periphery thereof, a primary coil Wound around said tube and confined within said groove, a secondary coil Wound around said tube outside of said primary coil and continuing longitudinally therebeyond, said primary coil being located within the first turns of wire at the low potential end of said secondary coil, and a rotor coil mounted in inductive relation to said secondary coil adjacent the high potential end of the latter.

6. A tunable radio frequency transformer comprising, in combination, a tube of insulating material provided with an annular groove extending around the periphery thereof, a

rimary coil wound around said tube and coned within said groove, a secondary coil wound around said tube outside of said primary coil and continuing longitudinally therebeyond, said primary coil being located Within the first turns of wire at the low otential end of said secondary coil, anotiier tube pivotally mounted within said iirst named tube adjacent to the low potential end of said secondary coil, and a rotor coil wound around said second-named tube and located in inductive relation to said secondary coil adjacent the high potential end of the latter. 7. radio frequency transformer comprising, in combination, a compacted primary coil, and a secondary coil positioned with its low potential end adjacent to and in inductive relation with said primary coil. 8. radio frequency transformer comprising, in combination, a compacted primary coil of superimposed layers of wire, a secondary coil positioned with its low potential end adjacent to and in close inductive relation to said primary coil, and a third coil in variable inductive relation to said secondary coil adjacent the high potential end of the latter.

9. radio frequency transformer comprising, in combination, a compacted primary coil, and a secondary coil whose low potential en d is positioned in close inductive relation with said primary coil, the primary coil being wound to present a small area to the secondry ary coil.

A radio frequency transformer coinprising, in combination, a compacted primary coil, and a secondary coil, the low potential end of the secondary coil being positioned adjacent to and in inductive relation to said primarycoil, the average diameter of the priin ary coil being approximately equal to the diameter of the low potential end of said secondary coil.

A'radio frequency transformer coniprising, in combination, a compacted primary lll coil, and a secondary coil, the low potential end of which is positioned in inductive relation to said p: imary coil and adjacent therev to, the length and depth of said primary coil being substantially equal, and its average diameter approximately the same as the diameter of the low potential end of said secondary coil.

12. A radio frequency transformer comprising, in combination, a compacted primary of relatively small gage wire, and a secondary coil of larger gage wire positioned with its low potential end adjacent to and in inductive relation to said primary coil.

13. A radio frequency transformer comprising, in combination, a compacted primary coil, and a secondary coil positioned in close inductive relation to said rimary coil, the average diameter of said prlmary coil closely approximating the internal diameter of said secondary coil.

In testimony whereof We have hereunto set our hands.

GLENN H. BROWNING. FREDERICK H. DRAKE. 

